JP2004035490A - Apparatus and method for producing aromatic polyisocyanate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for producing an aromatic polyisocyanate by which the aromatic polyisocyanate can be obtained stably over a long period by preventing the formation of a fixed material in a heat exchanger and the plugging of a pipe in the heat exchanger in a phosgenation reaction in the production of the aromatic polyisocyanate; and to provide a method for producing the aromatic polyisocyanate. <P>SOLUTION: The method for producing the aromatic polyisocyanate comprises a step for reacting an aromatic polyamine with phosgene, a step for cooling a vapor extracted from the reactor 1 by a heat exchanger 2, a step for separating the cooled fluid by a vapor-liquid separator 3 to a vapor component and a liquid component, and a step for refeeding the separated liquid component to the reactor 1. The aromatic amine is reacted with the phosgene in a solvent while spraying the solvent for preventing the aromatic polyisocyanate from dispersing from the reactor and flowing in the heat exchanger. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for producing an aromatic polyisocyanate. More specifically, the present invention relates to an aromatic polyisocyanate production apparatus and method for stably performing a phosgenation reaction in the production of an aromatic polyisocyanate for a long period of time.
[0002]
[Technical Background of the Invention]
Aromatic polyisocyanates such as tolylene diisocyanate (hereinafter abbreviated as TDI), diphenylmethane diisocyanate (hereinafter abbreviated as MDI), and methylene-crosslinked polyphenylene polyisocyanate (hereinafter abbreviated as polyMDI), which are important as raw materials for polyurethane, are commonly used. Are prepared by reacting an aromatic polyamine with phosgene in an inert solvent. For example, poly-MDI is obtained by reacting aniline with formaldehyde in the presence of an acid catalyst to react methylene-crosslinked polyphenylene polyamine (hereinafter abbreviated as poly MDA) with phosgene in a solvent such as monodichlorobenzene or orthodichlorobenzene. It is manufactured by Usually, such a phosgenation reaction of an aromatic polyamine is carried out using a production apparatus as shown in FIG.
[0003]
First, the manufacturing apparatus shown in FIG. 3 will be described. The production apparatus cools a gas extracted from a reactor 1 for reacting an aromatic polyamine and phosgene in a solvent in a gas-liquid coexistence state and a gas outlet 8a provided at an upper part of the reactor 1. And a reflux path for refluxing the obtained liquid component to the reactor 1.
The reflux path is generated by the gas outlet 8a and the pipe 8 for extracting gas constituting the gas phase in the reactor 1 to the outside of the reactor, the heat exchanger 2 for cooling the extracted gas, and cooling. A gas-liquid separator 3 for separating a mixed fluid of the condensed liquid and the non-condensed gas component into a gas component and a liquid component, and supplying the condensed liquid from the gas-liquid separator 3 to the reactor 1. And the piping 10 of the present invention.
[0004]
The reactor 1 includes a pipe 5 for supplying an aromatic polyamine or a solution containing an aromatic polyamine, a pipe 6 for supplying phosgene or a solution containing phosgene, a pipe 7 for supplying a solvent, A pipe 11 for extracting a reaction solution containing the generated aromatic polyisocyanate and a solvent is connected. Further, the reactor 1 may be equipped with a stirrer 4.
[0005]
Further, a pipe 9 for discharging a gas component is connected to the gas-liquid separation device 3.
Next, a method for producing an aromatic polyisocyanate using the production apparatus shown in FIG. 3 will be described. A solvent and an aromatic polyamine and phosgene as raw materials are supplied to a reactor 1. By stirring the supplied solvent, aromatic polyamine and phosgene with the stirrer 4 while controlling the temperature, the aromatic polyamine and phosgene are reacted to generate an aromatic polyisocyanate. At this time, hydrogen chloride is generated as a by-product. The generated aromatic polyisocyanate is extracted together with the solvent and phosgene, and is sent to the next step through the pipe 11.
[0006]
When the aromatic polyisocyanate is continuously produced, the solvent, the aromatic polyamine and phosgene are continuously supplied to the reactor, and the produced aromatic polyisocyanate is continuously withdrawn from the reactor.
Hydrogen chloride, vaporized phosgene and a solvent are present in the gas phase in the reactor 1. The gas in the gas phase in the reactor 1 is drawn out of the reactor from the gas outlet 8 a and introduced into the heat exchanger 2 through the pipe 8. The fluid cooled by the heat exchanger 2 is separated by the gas-liquid separator 3 into a gas component containing phosgene and hydrogen chloride and a liquid component containing a solvent and phosgene. The liquid component is re-supplied to the reactor 1 through the pipe 10, and the gas component is supplied to the phosgene absorption tower through the pipe 9.
[0007]
In the production of the aromatic polyisocyanate as described above, the liquid constituting the liquid phase in the reactor 1 is scattered into the gas phase due to stirring or bumping in the reactor 1, and a part of the scattered liquid is vaporized. It may flow into the heat exchanger 2 through the pipe 8 from the gas discharge port 8a together with the gas in the phase. When this liquid flows into the heat exchanger 2, solids adhere to the inner walls of the tubes in the heat exchanger 2, and during long-term operation of the apparatus, the tubes in the heat exchanger 2 are closed, and equipment management is performed. Has required a great deal of trouble.
[0008]
For this reason, in the production of the aromatic polyisocyanate, development of a production apparatus and a production method of the aromatic polyisocyanate which prevented the solid matter from adhering to the inner wall of the tube in the heat exchanger 2 was expected.
[0009]
[Object of the invention]
The present invention is intended to solve the problems associated with the prior art as described above, and is intended to prevent clogging of tubes in a heat exchanger in a phosgenation reaction in the production of an aromatic polyisocyanate, and to stabilize for a long period of time. It is an object of the present invention to provide a production apparatus and a production method for obtaining an aromatic polyisocyanate.
[0010]
Summary of the Invention
The present inventors have conducted intensive research to solve the above problems, and found that a solid substance attached to the inner wall of a tube in a heat exchanger is a reaction product of an aromatic polyisocyanate and hydrogen chloride contained in a scattered liquid. By spraying the solvent in the gas discharge channel of the reactor, it is possible to prevent the scattered liquid from flowing into the heat exchanger through the pipe from the gas discharge port accompanied by the gas in the gas phase. And found that it is possible to prevent solid matter from adhering to the inner wall of the tube in the heat exchanger.
[0011]
That is, the apparatus for producing an aromatic polyisocyanate according to the present invention includes a reactor for reacting an aromatic polyamine and phosgene in a solvent,
A reflux path for refluxing a liquid component obtained by cooling a gas extracted from a gas outlet provided at an upper portion of the reactor to the reactor,
The reflux path,
A heat exchanger for cooling the gas extracted from the gas outlet,
An apparatus for producing an aromatic polyisocyanate, comprising: a gas-liquid separator for separating a fluid cooled by the heat exchanger into a gas component and a liquid component,
In the gas discharge channel near the gas outlet of the reflux path, there is provided a solvent spraying device for spraying a solvent for preventing the aromatic polyisocyanate from scattering from the reactor and flowing into the heat exchanger. It is characterized by:
[0012]
The solvent spraying device preferably has a spray function. It is preferable that the solvent spraying device having the spraying function has a plurality of spray holes formed over substantially the entire radial direction of the gas discharge channel.
In the apparatus for producing an aromatic polyisocyanate according to the present invention, it is preferable that 0.1 to 10% of the total amount of the solvent supplied to the production apparatus is sprayed from the solvent spraying apparatus.
[0013]
Further, the method for producing an aromatic polyisocyanate according to the present invention comprises, in a solvent, at least an aromatic polyamine and phosgene, and a step of reacting the aromatic polyamine and phosgene in the solvent;
A step of extracting a gas constituting the gas phase in the reactor from a gas outlet provided in the upper part of the reactor, introducing the gas into a heat exchanger and cooling the gas,
Separating the fluid cooled by the heat exchanger into a gas component and a liquid component,
Re-supplying the liquid component to the reactor, the method for producing an aromatic polyisocyanate,
An aromatic polyisocyanate is prevented from scattering from the reactor and flowing into the heat exchanger from a solvent spraying device provided in a gas discharge channel for extracting gas in the reactor from the gas outlet. And reacting the aromatic polyamine and phosgene in the solvent while spraying the solvent.
[0014]
The solvent is preferably sprayed from the solvent spray device having a spray function, and the solvent spray device having the spray function having a plurality of spray holes formed over substantially the entire surface in the radial direction of the gas discharge channel. Preferably, it is sprayed from the device.
In the method for producing an aromatic polyisocyanate according to the present invention, it is preferable that 0.1 to 10% of the total amount of the solvent supplied to the reaction system is sprayed from the solvent spraying device.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described specifically.
[Aromatic polyisocyanate production equipment]
First, an apparatus for producing an aromatic polyisocyanate according to the present invention will be described with reference to FIG.
[0016]
As shown in FIG. 1, the apparatus for producing an aromatic polyisocyanate according to the present invention includes a reactor 1 for reacting an aromatic polyamine and phosgene in a solvent, and a gas exhaust provided at an upper portion of the reactor 1. A reflux path is provided for refluxing the liquid component obtained by cooling the gas extracted from the outlet 8 a to the reactor 1.
The reflux path includes a heat exchanger 2 for cooling the gas extracted from the gas outlet 8a, and a gas-liquid separator 3 for separating the fluid cooled by the heat exchanger 2 into a gas component and a liquid component. And
[0017]
The reactor 1 is not particularly limited as long as it is a general reactor used in the production of aromatic polyisocyanate, but a pipe 5 for supplying an aromatic polyamine or a solution containing an aromatic polyamine, and phosgene or phosgene are supplied. It is preferable that a pipe 6 for supplying a solution containing the solvent, a pipe 7 for supplying a solvent, and a pipe 11 for extracting a reaction solution containing the generated aromatic polyisocyanate and the solvent be connected. Further, the reactor 1 is preferably provided with a stirrer 4.
[0018]
The reactor 1 has a gas outlet 8a for discharging a gas constituting the gas phase in the reactor 1. The gas outlet 8a is connected to a pipe 8 for introducing the gas discharged from the reactor 1 into the heat exchanger 2.
As shown in FIG. 2, an aromatic polyisocyanate is prevented from being scattered from the reactor 1 and flowing into the heat exchanger 2 in the gas discharge channel near the gas discharge port 8 a in the pipe 8. A solvent spraying device 13 for spraying the solvent is provided. The solvent spraying device 13 preferably has a spray function. It is preferable that the solvent spraying device 13 having the spraying function has a plurality of spray holes formed over substantially the entire radial direction of the gas discharge channel.
[0019]
When the solvent is sprayed into the reactor 1 using the solvent spraying device 13, the liquid scattered by stirring or bumping in the reactor 1 collides with the scattered solvent and falls into the liquid phase in the reactor 1. However, it is possible to prevent the heat from flowing into the heat exchanger 2 through the pipe 8.
Further, it is possible to prevent the scattered liquid from colliding with the solvent spraying device 13 and flowing into the heat exchanger 2 through the pipe 8, and to remove the liquid component attached to the solvent spraying device 13 due to the collision by spraying the solvent. You can also.
[0020]
In the apparatus for producing an aromatic polyisocyanate according to the present invention, 0.1 to 10%, preferably 0.1 to 8% of the total amount of the solvent supplied to the production apparatus is sprayed from the solvent spraying apparatus 13. Is preferred. The ratio of the solvent to be sprayed is preferably small as long as the amount of the solvent to be sprayed can prevent the aromatic polyisocyanate from scattering from the reactor 1 and flowing into the heat exchanger 2.
[0021]
The heat exchanger 2 is used to cool the gas discharged from the gas discharge port 8a of the reactor 1, and is not particularly limited as long as it is a general heat exchanger used in the production of aromatic polyisocyanate. For example, a multi-tube heat exchanger is used. In the multi-tube heat exchanger, a large number of tubes are provided in the heat exchanger, and a fluid passing through the tubes is cooled by bringing the tubes into contact with a coolant such as cooling water. The heat exchanger 2 is connected to a pipe 8.
[0022]
The gas-liquid separation device 3 is a device that is used to separate the fluid cooled by the heat exchanger 2 into a gas component and a liquid component, and can separate and extract the gas component and the liquid component. There is no particular limitation. The gas-liquid separator 3 is connected to a pipe 10 for re-supplying the liquid component to the reactor 1. Further, it is preferable that a pipe 9 for discharging a gas component is connected.
[0023]
The pipe 10 is not particularly limited as long as the liquid component can be resupplied to the reactor 1. The pipe 10 is connected to the pipe 10 between the gas-liquid separation device 3 and the reactor 1, and the liquid component is supplied to the reactor 1. A liquid feeding means such as a pump for supplying the liquid may be provided.
[Method for producing aromatic polyisocyanate]
Next, a method for producing an aromatic polyisocyanate according to the present invention will be described.
[0024]
The method for producing an aromatic polyisocyanate according to the present invention comprises, in a solvent, at least supplying an aromatic polyamine and phosgene, and reacting the aromatic polyamine and phosgene in the solvent; Extracting a gas constituting the gas phase in the reactor from a gas outlet provided in the reactor, introducing the gas into a heat exchanger to cool the gas, and converting the fluid cooled by the heat exchanger into a gas component and a liquid. A method for producing an aromatic polyisocyanate, comprising: a step of separating the liquid component into components; and a step of re-supplying the liquid component to the reactor, wherein gas is discharged from the gas outlet to discharge gas in the reactor. While spraying a solvent for preventing the aromatic polyisocyanate from being scattered from the reactor and flowing into the heat exchanger from the solvent spraying device provided in the flow path, the aromatic polyisocyanate is dispersed in the solvent. A process for producing an aromatic polyisocyanate, wherein the reaction of amine with phosgene.
[0025]
Such a method for producing an aromatic polyisocyanate is desirably carried out using the above-described apparatus for producing an aromatic polyisocyanate according to the present invention, and has an apparatus capable of spraying a solvent in the gas discharge channel. There is no particular limitation on the manufacturing apparatus.
<Aromatic polyamine>
The aromatic polyamine that can be used in the present invention is not particularly limited as long as it can be used in the production of ordinary aromatic polyisocyanate, and examples thereof include tolylenediamine, diphenylmethanediamine, and methylene-crosslinked polyphenylenepolyamine. The aromatic polyamine may be one produced by a usual method. For example, a methylene-crosslinked polyphenylene polyamine can be produced by reacting aniline with formaldehyde in the presence of an acid catalyst such as hydrochloric acid.
[0026]
Further, the aromatic polyamine can be used by dissolving it in a solvent used in a phosgenation reaction of the aromatic polyamine.
<Phosgene>
The phosgene that can be used in the present invention is not particularly limited as long as it is used in the production of ordinary aromatic polyisocyanate, and contains hydrogen chloride as long as it does not affect the phosgenation reaction. Is also good.
[0027]
The phosgene can be used by dissolving it in a solvent used in a phosgenation reaction of an aromatic polyamine.
<Solvent>
The solvent that can be used in the present invention is not particularly limited as long as it is used in a usual aromatic phosgenation reaction of an aromatic polyamine. Examples thereof include aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as chlorotoluene, chlorobenzene and dichlorobenzene, esters such as butyl acetate and amyl acetate, and ketones such as methyl isobutyl ketone and methyl ethyl ketone.
[0028]
The solvent used to prevent the aromatic polyisocyanate from scattering from the reactor and flowing into the heat exchanger may be the same as the solvent used in the reaction step between the aromatic polyamine and phosgene. preferable.
<Method for producing aromatic polyisocyanate>
Hereinafter, a method for producing an aromatic polyisocyanate according to the present invention will be described with reference to FIG.
[0029]
First, the raw material aromatic polyamine or a solution containing the aromatic polyamine is supplied to the reactor 1 from the pipe 5, the raw material phosgene or a solution containing the phosgene is supplied from the pipe 6, and the solvent is supplied from the pipe 7 to the reactor 1. Further, the solvent is sprayed from the solvent spraying device 13 in the gas discharge channel near the gas outlet in the pipe 8. The solvent is preferably sprayed from a solvent spraying device 13 having a spraying function, and from the solvent spraying device 13 having a spraying function having a plurality of spray holes formed over substantially the entire surface in the radial direction of the gas discharge channel. More preferably, it is sprayed.
[0030]
While the liquid phase in the reactor 1 is stirred by the stirrer 4, the inside of the reactor 1 is heated or cooled to adjust to a desired temperature. As a result, the aromatic polyamine reacts with phosgene to produce an aromatic polyisocyanate in the liquid phase in the reactor 1. The temperature and pressure of the phosgenation reaction are not particularly limited as long as they are ordinary temperatures and pressures for phosgenating an aromatic polyamine. The aromatic polyisocyanate obtained by the reaction is extracted together with the solvent and phosgene, and sent to the next step through the pipe 11.
[0031]
When the aromatic polyisocyanate is continuously produced, it is preferable that the solvent, the aromatic polyamine and phosgene are continuously supplied to the reactor, and the generated aromatic polyisocyanate is continuously discharged from the reactor.
In the reactor 1, the liquid in the liquid phase is scattered into the gas phase due to stirring, bumping, etc., but by spraying the solvent in the gas discharge channel, the scattered liquid collides with the scattered solvent and the reactor is scattered. 1 can be prevented from falling into the liquid phase and flowing into the heat exchanger 2 through the pipe 8, and the pipes in the heat exchanger 2 can be prevented from being blocked.
[0032]
Further, it is possible to prevent the scattered liquid from colliding with the solvent spraying device 13 and flowing into the heat exchanger 2 through the pipe 8, and to remove the liquid component attached to the solvent spraying device 13 due to the collision by spraying the solvent. You can also.
The amount of the solvent sprayed from the solvent spraying device 13 is 0.1 to 10%, preferably 0.1 to 8% of the total amount of the solvent supplied to the reaction system. The ratio of the solvent to be sprayed is preferably small as long as the amount of the solvent to be sprayed can prevent the aromatic polyisocyanate from scattering from the reactor 1 and flowing into the heat exchanger 2.
[0033]
In this phosgenation reaction, hydrogen chloride is generated as a by-product. The generated hydrogen chloride exists in the gas phase of the reactor 1. Further, a vaporized solvent and phosgene are also present in the gas phase of the reactor 1. The gas in the gas phase in the reactor 1 is extracted out of the reactor through the gas outlet 8a, introduced into the heat exchanger 2 through the pipe 8, and cooled.
Next, the gas extracted from the gas discharge port 8a is cooled by the heat exchanger 2. By the cooling in the heat exchanger 2, at least a part of the solvent and phosgene in the gas is condensed into a liquid component. The cooled fluid is introduced into the gas-liquid separator 3.
[0034]
In the gas-liquid separation device 3, the introduced fluid is separated into a gas component containing phosgene and hydrogen chloride and a liquid component containing a solvent and phosgene. The liquid component is re-supplied to the reactor 1 through the pipe 10, and the gas component is supplied to the phosgene absorption tower through the pipe 9.
[0035]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the examples.
[Preparation of methylene crosslinked polyphenylene polyamine]
97% aniline and 37% formaldehyde aqueous solution were subjected to a condensation reaction at a temperature of 30 to 120 ° C in the presence of 35% hydrochloric acid. The resulting reaction solution was neutralized by adding a 32% aqueous sodium hydroxide solution, and an oil phase was taken out. After the taken-out oil phase was washed with hot water, water and unreacted aniline were distilled off under reduced pressure to obtain methylene-crosslinked polyphenylenepolyamine (hereinafter abbreviated as polyMDA).
[Production of methylene crosslinked polyphenylene polyisocyanate]
Production of methylene-crosslinked polyphenylene polyisocyanate (hereinafter abbreviated as polyMDI) was carried out using the production apparatus shown in FIG. 27.6 kg / h of a 20 mass% poly-MDA orthodichlorobenzene (hereinafter abbreviated as ODCB) solution, 23.7 kg / h of phosgene, and 18.7 kg / h of ODCB as a solvent were supplied to the reactor 1. The reaction temperature was maintained at 80 ° C. with a jacket and an external heater, and the pressure was maintained at 5.0 kg / cm ² (gauge pressure). 1.6 kg / h of ODCB was supplied to the solvent spraying device 13 through the pipe 12, and ODCB was sprayed in the gas discharge channel near the gas discharge port 8 a in the pipe 8. The reaction solution in the reactor 1 was continuously taken out, and the produced poly-MDI was recovered. Even if the above operation was continuously performed for a long period, no blockage of the pipe in the heat exchanger 2 was observed.
[0036]
[Comparative example]
[Production of methylene crosslinked polyphenylene polyisocyanate]
Poly MDI was manufactured using the manufacturing apparatus shown in FIG. The production of poly-MDI was carried out in the same manner as in Example, except that ODCB was supplied as a solvent to the reactor 1 at 20.3 kg / h without using the solvent spraying apparatus.
[0037]
After 3 to 4 months from the start of the operation, a blockage of the tube in the heat exchanger 2 was observed.
[0038]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the manufacturing apparatus and manufacturing method of aromatic polyisocyanate which concerns on this invention, in the phosgenation reaction of manufacture of aromatic polyisocyanate, generation | occurrence | production of the fixed substance in a heat exchanger and blockage of the tube in a heat exchanger are prevented. And an aromatic polyisocyanate can be stably obtained over a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic view of an apparatus for producing an aromatic polyisocyanate according to the present invention.
FIG. 2 is an enlarged view of the vicinity of a gas outlet shown in FIG.
FIG. 3 is a schematic view of a conventional apparatus for producing an aromatic polyisocyanate.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 reactor 2 heat exchanger 3 gas-liquid separator 4 stirrer 5-12 pipe 8a gas outlet 13 solvent sprayer

Claims (8)

A reactor for reacting the aromatic polyamine and phosgene in a solvent,
A reflux path for refluxing a liquid component obtained by cooling a gas extracted from a gas outlet provided at an upper portion of the reactor to the reactor,
The reflux path,
A heat exchanger for cooling the gas extracted from the gas outlet,
An apparatus for producing an aromatic polyisocyanate, comprising: a gas-liquid separator for separating a fluid cooled by the heat exchanger into a gas component and a liquid component,
In the gas discharge channel near the gas outlet of the reflux path, there is provided a solvent spraying device for spraying a solvent for preventing the aromatic polyisocyanate from scattering from the reactor and flowing into the heat exchanger. An apparatus for producing an aromatic polyisocyanate, comprising: The apparatus for producing an aromatic polyisocyanate according to claim 1, wherein the solvent spraying apparatus has a spray function. The aromatic polyisocyanate manufacturing apparatus according to claim 2, wherein the solvent spraying device having the spraying function has a plurality of spray holes formed over substantially the entire surface in a radial direction of the gas discharge channel. . The aromatic solvent according to any one of claims 1 to 3, wherein 0.1 to 10% of the total amount of the solvent supplied to the aromatic polyisocyanate production device is sprayed from the solvent spray device. Equipment for producing polyisocyanate. In a solvent, at least, an aromatic polyamine and phosgene are supplied, and a step of reacting the aromatic polyamine and phosgene in the solvent,
A step of extracting a gas constituting the gas phase in the reactor from a gas outlet provided in the upper part of the reactor, introducing the gas into a heat exchanger and cooling the gas,
Separating the fluid cooled by the heat exchanger into a gas component and a liquid component,
Re-supplying the liquid component to the reactor, the method for producing an aromatic polyisocyanate,
An aromatic polyisocyanate is prevented from scattering from the reactor and flowing into the heat exchanger from a solvent spraying device provided in a gas discharge channel for extracting gas in the reactor from the gas outlet. A method for producing an aromatic polyisocyanate, comprising reacting an aromatic polyamine with phosgene in a solvent while spraying a solvent for the method. The method for producing an aromatic polyisocyanate according to claim 5, wherein the solvent spraying device has a spray function. The method for producing an aromatic polyisocyanate according to claim 6, wherein the solvent spraying device having the spray function has a plurality of spray holes formed over substantially the entire surface in the radial direction of the gas discharge channel. . The method for producing an aromatic polyisocyanate according to any one of claims 5 to 7, wherein 0.1 to 10% of the total amount of the solvent supplied to the reaction system is sprayed from the solvent spraying device.

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